//
// Copyright (c) 2017 anygone contributors (see AUTHORS file)
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice, this
//   list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
//
// * Neither the name of anygone nor the names of its
//   contributors may be used to endorse or promote products derived from
//   this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//

package main

import (
	"fmt"
	"net"
	"os"
	"path/filepath"
	"strings"

	"github.com/spf13/pflag"
)

type IPAddrCIDR struct {
	Net   net.IPNet
	Valid bool
}

func (ipnet IPAddrCIDR) String() string {
	if ipnet.Valid {
		return ipnet.Net.String()
	}
	return ""
}

func (ipnet *IPAddrCIDR) Set(value string) error {
	ip, net, err := net.ParseCIDR(strings.TrimSpace(value))
	if err != nil {
		return err
	}
	net.IP = ip
	*ipnet = IPAddrCIDR{*net, true}
	return nil
}

func (*IPAddrCIDR) Type() string {
	return "ipNet"
}

type Config struct {
	name  string
	flags *pflag.FlagSet

	Help       bool
	Version    bool
	DeviceName string
	DeviceType string
	IFConfig   IPAddrCIDR
	PostUp     string
}

func (cfg *Config) PrintUsage() {
	cfg.flags.Usage()
}

func (cfg *Config) PrintVersion() {
	fmt.Println("anygone version 0.1")
}

func (cfg *Config) Dump() {
	fmt.Printf("Config: %+v\n", cfg)
}

func (cfg *Config) parsePost() error {
	extraArgs := cfg.flags.Args()
	if len(extraArgs) > 0 {
		return fmt.Errorf("unknown additional parameters (%s)", strings.Join(extraArgs, ", "))
	}

	if cfg.DeviceName == "" && cfg.DeviceType == "" {
		cfg.DeviceType = "tun"
	}
	return nil
}

func NewConfig() (cfg *Config, err error) {
	cfg = &Config{}
	cfg.name = filepath.Base(os.Args[0])
	cfg.flags = pflag.NewFlagSet(cfg.name, pflag.ContinueOnError)
	cfg.flags.SetInterspersed(false)
	cfg.flags.SortFlags = false
	cfg.flags.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage of %s:\n", cfg.name)
		cfg.flags.PrintDefaults()
	}

	cfg.flags.BoolVarP(&cfg.Help, "help", "h", false, "print this...")
	cfg.flags.BoolVarP(&cfg.Version, "version", "v", false, "print version info and exit")

	cfg.flags.StringVarP(&cfg.DeviceName, "dev", "d", "", "device name")
	cfg.flags.StringVarP(&cfg.DeviceType, "type", "t", "", "device type")
	cfg.flags.VarP(&cfg.IFConfig, "ifconfig", "n", "the local address for the tun/tap device and the used prefix length")
	cfg.flags.StringVarP(&cfg.PostUp, "post-up-script", "x", "", "script gets called after interface is created")

	if err = cfg.flags.Parse(os.Args[1:]); err != nil {
		return
	}
	err = cfg.parsePost()
	return
}